1. Field of Invention
This invention relates to pressure measuring apparatus which generate frequency signals corresponding to the pressure being measured; and more particularly, to such apparatus comprising a diaphragm to which pressure is applied and a resilient vibrator linked to the diaphragm for measuring the pressure by utilizing variations in the natural frequency of the vibrator.
2. Description of Prior Art
FIG. 1 is a cross sectional view of a conventional pressure measuring apparatus, such as disclosed in Japan Laid Open Pat. No. 1981-79221, wherein a diaphragm 1 is subjected to pressure P.sub.2 to be measured with reference pressure P.sub.1 being applied to the body shell 2 containing the vibrator 3, a tabular vibrator 3 has one end thereof secured to the inner wall of shell 2 and the other end thereof secured to diaphragm 1 and a circuit 4 detects the natural frequency of tabular vibrator 3. With this conventional apparatus, it is possible to obtain high pressure sensitivity and digital output signals corresponding to pressure to be measured which are readily adaptable for computer usage.
However, disadvantageously, this type of conventional pressure measuring apparatus has many problems. For example, the securing of vibrator 3 to diaphragm 1 presents a problem. Rectilinearity (i.e. relationship between applied pressure and generated force) is deteriorated by the distortion caused when securing the members to each other, for instance, by welding. Another example is that the natural frequency of diaphragm 1 is bound to approach that of vibrator 3. Thus, a device must be used to prevent this concurrence of frequencies. A further example is that the stress generated in a connecting parts between the diaphragm and vibrator must be minimized.